AUDIOPHILE DEBATE: OTL – The mistrusted valve amplifier?

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Grumbling women

The thread starts:  I have heard, as probably have most valve aficionados, of scare stories of OTLs going faulty and blowing speakers, though a lot of DIY'ers still make them. For me the sound is sublime but there are limitations to speaker compatibility.  I'm currently thinking along the lines of a design for a 10W low cost, easy to use and safe OTL:

Low cost One of the areas where a cost saving is made is of course the absence of the output transformer, always a big expense to achieve great performance with a traditional valve amp. With suitable connections between them the power supply requirements can be met with two off the shelf transformers, cost £76.

Valve choice is always going to have an impact but there are some low cost options around at the moment. 2 off 6080 per channel will give 10W and there are some available for £6 each, and using 6J6 for input and driver stages will only cost $3 per valve.

Ease of use Some people may find the requirement of having to bias an amplifier a chore or even a PITA, so I am working on an auto-bias scheme that will need no adjustment at all.  I haven't come across an OTL that offers this as yet.

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